A Robust Method Detecting Perchlorate in Water
While the U.S. Environmental Protection Agency and state agencies continue to gather and review risk and impact data on acceptable levels...
While the U.S. Environmental Protection Agency and state agencies continue to gather and review risk and impact data on acceptable levels of perchlorate in drinking water supplies, Scott McLean, director of research and development at Alpha Analytical Labs, in Westborough, MA, and his assistant, Arin Jones, analyze perchlorate levels in drinking and wastewater samples from clients in both public and private sector industries. After testing hundreds of samples, McLean, co-founder of the environmental analysis company, has concluded that a tandem mass spectrometry system from Applied Biosystems/MDS SCIEX contributes greatly to the ability of EPA Method 332 to detect low levels of perchlorate in both drinking and industrial wastewater samples.
Sources of Perchlorate
Perchlorate is a highly mobile, water-soluble compound. As such, it’s capable of migrating through the environment in the ground and surface water easily. If perchlorate is introduced into the environment, for example, through industrial discharge, explosive or fireworks detonation, it has the potential of contaminating ground and surface water. As perchlorate moves with surface and groundwater, it contaminates soil, drinking, and irrigation water, making testing and proper disposal of perchlorate a significant concern for a number of industries.
As a major component in many different explosive devices, perchlorate is released into the environment by military sites, and manufacturers of rocket engines, fireworks, road flares and air bag inflators. Any industry employing perchlorate salts or acids can potentially discharge it to the environment. Agricultural industries that grow produce near sources of perchlorate, use perchlorate contaminated fertilizer (e.g., Chilean nitrate), or irrigate with perchlorate tainted water − risk contaminating their product through bioaccumulation.
Operators of wastewater treatment plants that use chlorine and chloramines may find their effluents contaminated with unacceptable concentrations of perchlorate. Treatment plants that use hypochlorite to sterilize and oxidize organics during treatment of wastewater and drinking water may also be susceptible to perchlorate contamination.
According to McLean, it’s sometimes more difficult to analyze industrial wastewater than drinking water due to the complex matrices of the effluent. “One waste stream that we test is composed of hydrochloric, sulfuric and perchloric acid - the source of the perchlorate - and ammonium hydroxide. It has a high conductivity, and is loaded with sulfates and other components,” he explains.
Perchlorate Testing Services
In 1999, the EPA established the Unregulated Contaminant Monitoring Rule (UCMR), placing perchlorate on a list of analytes that the agency would then monitor in drinking water supplies throughout the country for the next couple of years. Due to the uncertainty associated with the health risks of perchlorate, it also has been included on the UCMR2 list of analytes to be analyzed starting in 2007. High levels of perchlorate are known to interfere with production of thyroid hormone, which can impair normal growth and development of fetuses and infants, and may also result in thyroid gland tumors after chronic exposure to the chemical.
The EPA has established an Official Reference Dose - based on an individual’s weight - of 0.0007 mg/kg/day of perchlorate that each person can safely ingest. This level is consistent with the National Academy of Science’s (NAS) recommendation of January 2005. The agency has not yet established a federal maximum contaminant limit (MCL) in drinking water, pending review of alternate sources of ingestion. Some states, including Massachusetts, Maryland, New Mexico, Texas, California, Nevada and Arizona have set their own limits for perchlorate.
In 2004, Alpha Analytical Labs fortified its perchlorate testing services in response to a MA Department of Environmental Protection (MADEP) emergency regulation mandating all Public Water Supplies (PWS) test for the compound. MADEP specified using the EPA-approved Method 314 with modifications designed to lower the reporting limit to 1 μg/L (ppb). The emergency regulation was enacted in part based on concerns raised by the discovery of low levels of perchlorate in drinking water wells in the town of Bourne, which borders the Massachusetts Military Reservation on Cape Cod.
In that same year, the U.S. Department of Defense (DOD) Environmental Data Quality Workgroup mandated that all perchlorate test results greater than regulatory or permit levels at military sites be confirmed by use of a mass spectrometry or other definitive method of detection. At this time, Alpha Analytical Labs, an EPA-certified lab for perchlorate testing, began investigating the use of a tandem mass spectrometry system for performing the EPA-approved Method 332 for perchlorate analysis in a variety of water samples.
Method 332 is Sensitive and Robust
Methods 314 and 332 are two EPA-approved methods for perchlorate detection that Alpha Analytical Labs uses in the testing of drinking water and industrial wastewater samples. Both of these methods use ion chromatography (IC) and are capable of detecting sub-ppb levels of perchlorate. According to McLean, however, Method 332 (see www.epa.gov/nerlcwww/m_332_0.pdf) is more sensitive than Method 314 (see www.epa.gov/safewater/methods/sourcalt.html), and, unlike 314, 332 isn’t impacted by elevated concentrations of common anions present in water samples.
“Using Method 314, if a sample has a conductivity [measurement] over 400μS/cm, we have to treat that sample through cartridges that remove common ions, specifically sulfate, carbonate, and chloride. All QC samples associated with the offending sample must also be treated through the cleanup columns. Then all the samples are retested,” says McLean.
Applying Method 332, Alpha Analytical Labs has tested water samples with conductivities as high as 32,000 μS/cm without their results being negatively impacted.
The key difference between Methods 314 and 332 is that, in Method 332, Alpha Labs employs a tandem mass spectrometry instrument - the Applied Biosystems/MDS SCIEX API 2000TM MS/MS System - as the detector to the Dionex ICS 2500 system. A tandem mass spectrometer effectively reduces interference from common anions that contribute to the complexity of the sample matrix and hinder accurate identification of the target analyte.
“The main reason we use the IC/MS/MS method is that it removes interferences associated with the sample matrix. The other reason is the enhanced sensitivity of the API 2000 System; using IC/MS/MS for Method 332 our detection limit, (after calibration), is about 25 times lower than is possible with Method 314,” notes McLean.
Using Method 332, Alpha Analytical Labs has achieved lower detection limits for perchlorate in water, soil, solid material, as well as wastewater samples, than were possible with Method 314.
“From an analytical standpoint, using IC together with the Applied Biosystems MDS/SCIEX API 2000 System makes the analysis of complex matrices very easy, whether it is a ground water sample, or an industrial effluent sample,” says McLean.
About the Author: Mark Springer is a senior science writer for Applied Biosystems, with headquarters in Foster City, CA. Contact: 650-570-6667, email@example.com or www.appliedbiosystems.com.